US2271645A - Catalytic cracking of hydrocarbons - Google Patents

Description

Feb. 3, 194,2. E. R. KANHoFER A l 2,271,645

GATALYTIC CRACKING OF HYDROCARBONS Filed Jan. 22. 1940 Z UNE i /6 I /J fL/ISH 7L j CHAMBER X26 20A/E las CATALYTIC CRACKING F HYDROCARBONS y I Elmer R. Kanhofer, Chicago, Ill., assgnor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application January 22, 1940, serial No. 314,943 v Patented Feb. 3, 1.942

UNITED STATE 4 Claims.

This invention relates to a process for converting hydrocarbon oil into valuable products including high anti-knock gasoline by treatment of said hydrocarbon oil with a powdered catalytic agent under suitable conditions to bring about cracking thereof.

(ci. lss-4s) The use of catalytic agents to assist the thermal decomposition of hydrocarbon oils such' as those of petroleum origin into high yields of gasoline and other valuable products has been practiced. Among the agents employed are the reduced -metal catalysts including iron, cobalt, nickel, etc., which are subject to a number of disadvantages including the fact that they are poisoned by sulfur compounds which. may be present in oils undergoing conversion, and furthermore that they tend to promote gas and carbon-forming reactions with the net result that the catalyst life is comparatively short. Another type of cracking catalyst is the activated earth type in which naturally occurring clays are used which have been treated with acids 'or other.

chemicals toincrease their catalytic activity.

Still another type of catalyst is made up of activated alumina or magnesia which may have deposited thereon various promoting oxides from the left-hand column of the 4th, 5th and 6th groups of the Periodic Table and include particularly such oxides as those of chromium, molybdenum, vanadium, etc.

A further type of catalyst, which is the preferred material of this invention is the so-called silica-alumina, silica-zirconia and silica-aluminazirconia composite which is manufactured by the separate or simultaneous precipitation of the component compounds followed by washing, drying and calcining steps whereby a finished catalyst is prepared. The catalysts are prepared under such conditions that alkali-metal ions are substantially eliminated in order to obtain adequate catalytic `activity and stability insofar as an extended life is concerned.

In one specific embodiment the present invention comprises a process for converting hydrocarbon oil into valuable products including high antiknock motor f-uel which comprises charg.- ing said hydrocarbon oil to a fractionator, removing an intermediate boiling fraction therefrom. passing said fraction together with a powdered cracking catalyst Ato a primary cracking zone 4under conditions of temperature and pressure adequate to effect substantial catalytic cracking thereof, returning the reaction products together with partially spent catalyst in suspension to said fractionator, removing thev fractionator bottomsI` containing said partially spent catalyst in suspension, passing said bottoms to a secondary cracking zone under conditions of temperature and pressure adequate toeffect substantial catalytic cracking' thereof, supplying the reaction products containing spentcracking catalyst in suspension to a flashing zone, removing a vaporous portion of said reaction products from the flashing zone and returning them to said fractionator, withdrawing a residualportion of said reaction products containing spent cracking cata-v lyst in suspension, and recovering the gasoline and gas from said fractionator. l

The process is illustrated in diagrammatic form in the attached drawingwhich has not been made to scale nor has any attempt been made to proportionate the various parts of the equipment. y Hydrocarbon oil such as a distillate fraction of petroleum or other hydrocarbon oil, crude oil or topped crude oil is introduced through line I, valve 2, pump 3, heat exchanger 4, .valve 5 and fractionator 6. Anintermediate boiling fraction which may comprise kerosene, gas, oil, naphtha or a distillate including this entire boiling range of oils is withdrawn through line l, valve 8, pump 9, and valve/I0 to primary crack- 'ing zone I I. Powdered catalytic material may be introduced from catalyst charger I2 through line I3 and valvel Il. The primary cracking zone II may consist of a preheating coil followed by a suitable reactor which may be any type of reactor adaptable to use with powdered catalysts. This includes a `tubular coil disposed in a heating zone or a vertical type of reactor containing contacting members such as bailles, bubble f trays, etc. The catalytic cracking step is carried out at a temperature within the range of 500- 1200 F.- and a pressure of the order of 50-1000 pounds per square inch or higher. The exact choice of conditions will depend to a large extent upon the stock being processed and the character of theproduct which isto be obtained. For example, when operating at relatively elevated pressures of the order of -1000 pounds per square inch and a temperature of about 500- 900 F., a substantially olen-free gasoline is produced. When operating at temperatures in excess of 900 F., a more olenic type of gasoline is produced. The latter type usually has a. somewhat higher octane number and the former type of gasoline is more suitable for use in aviation motor fuels because of the low olen content and ythe relatively higher susceptibility to tetraethyl lead. The reaction products including the'pnntially spent catalyst are withdrawn through line `I5, valve I6 and line I1 to fractionator i. Gasoline and gas are removed through line- Il and valve I9 through suitable heat exchangers, condensers, etc., not shown in interests of simplifying the drawing. Fractionator bottoms are withdrawn through line 20, pump 20' and valve 2l to the secondary cracking zone 22 which may be similar in construction to the' primary cracking' zone I I or may be somewhat diierent in order to compensate for the diierent. character of the mary cracking zone, but need not be exactly the same 'as those chosen for the primary zone, but instead may be suitably adjusted to permit optimum loperation for'a stock of the character ofl that being charged and also to compensate for thefreduced activity of the cracking catalyst whichhas been partially spent by use lin the primary. step. The'conditions here will also dependrupon the stock being processed and the character of the products desired. In general when heavy oils are being charged so that the fractionator. bottoms are of a high boiling type somewhat milder conditionsare employed than in the primary zone wherein the lower boiling and consequently more refractory oils are processed. n the other hand, the activity of the catalyst is somewhat reduced so that itlmay be necessary to increase the temperature or to decrease the space velocity somewhat in order to obtain ing arewithin the range mentioned for the priof the distance from the bottom of the flash chamber so that the vaporous portion passes upward through the liquid residue. The vapors are returned to the fractionator and the residue containing spent catalyst in suspension is withdrawn from the ash chamber. The cracking .catalyst may be separated and reactivated by treatment with an oxygen-containing gas at a temperature of 1000 F. The reactivated catalyst may then be returned to the system. The separated oil is suitable for use asan industrial fuel oil. .A 400 F. end point gasoline of 77 octane number is obtainable. In addition, a gas containing polymerizable gaseous olefins is obtained which is a source of additional high antiknock motor fuel. The total yield of gasoline including that produced from the polymers may amount to 63% of the'orig'inal charge.

adequate conversion.Y Line-23 and valve 2l serve as a means of draining fractionator 6 or of withdrawing a portion of the fractionator bottoms.

The reaction products from secondary cracking zone 2-1 pass through line 25 and valve 26 to ilash chamber 21. Normally the products are introduced near the bottom ofthe flash chamber at a point kbelow the surface of a liquid level maintained therein. This assists in keeping the catalyst in suspension, thus preventing plugging of the outlet line and also permits additional reaction since the temperature maintained is usually within the' range at which some catalytic cracking will occur. The spent catalyst suspended in residual oil is withdrawn through line 2l and valve '29 to a suitable separator from which the catalyst is recovered and may be reactivated by treatment with an oxygen-containing gas at a temperature in excess of 900 F. to remove carbonaceous deposits therefrom. Theresidual oil may be used for fuel or may be coked in a separate coking apparatus. A vaporous portion of the reaction products pass from flash chamber 21 throughline 3l, valve 3| and 'line I1 to fractionator 6. The gasoline produced in this step together with that from'A the primary step is removed as previously described through line I8 and valve I9.

The following example is given to illustrate the usefulness and practicability of my process, but should not beA construed as limiting it to the exact conditions indicated therein.

-A topped Mid-Continent crude oil may be charged to the fractionator as described and a fraction boiling within the range of approximately 40G-800" F. removed, mixed with a finely divided silica-alumina cracking catalyst and cracked at a temperature of 975 F. and an average pressure ofA 200 pounds per square inch. Ap-

n .proximately 6% by weight of catalyst may be used and the catalyst introduced into the oil inthe form of a slurry in a small amount of water. The reaction products are returned to the fractionator and a residual fraction withdrawn to the secondary cracking zone which may comprise a tubular .coil disposed in a heating zone and which may. be maintained at a-temperature of 932F.v and a pressure of. 250 pounds per square inch. The reaction products are passed to the flash .chamber which is maintained at a temperature of 875.F. anda pressure of 50 pounds Der square inch. A liquid level may be maintained in the ash lchamber and the reaction products introduced at a point about one-fourth I claim as my invention: l. A hydrocarbon oil conversion process which 4 comprises introducing the charging oil to a fraccatalyst to the fractionating zone, thereby commingling the catalyst with said residual fraction, removing' the admixed residual fraction and catalyst' from the fractionating zone and subjecting the same to independently controlled cracking conditions, separating the products of the lastmentioned step into vapors and residue, and supplying the separated vapors to the fractionating zone.

2. The process of claim 1 wherein the powdered crackingfcatalyst is selected from the group consisting of silica-alumina, silica-zirconia and silica-aluminazirconia.

3. The process as set forth in claim l wherein the ilrst and second-mentioned cracking steps are operated at a temperature within the range of approximately 500l200 F. and a pressure Within the range of approximately 50-1000 pounds per square inch.

4. A hydrocarbon oil conversion process which comprises introducing the charging oil to a fractionating zone and therein fractionating the same together with cracked products, formed as hereinafter set forth, to form a gasoline-containing overhead product, a residual fraction containing unvaporized charging oil, and a condensate fraction boiling intermediate said overhead product and residual fraction, commingling a powdered cracking catalyst with said intermediate condensate fraction and subjecting the resultant mixture to catalyticlcracking conditions, introducing the resultant conversion products and admixed catalyst to the fractionatingzone, thereby commingling the catalyst with said residual fraction, removing the admixed residual fraction and catalyst from the fractionating zone and subjecting the same to independently controlled cracking conditions, reducing the pressure on the products of the last-mentioned step and separating the same into vapors and residue, and supplying the separated vapors to the fractionating zone.

ELMER R. KANHOFER.

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